20110023_Environmental Assessment_20100609 (5)

Appendix C
Amended Description of
Parallel Bridge Corridor
Alternatives with NC 12
Maintenance Selected for
Detailed Study
C. Amended Description of Parallel
Bridge Corridor Alternatives with
NC 12 Maintenance Selected for
Detailed Stu
This section amends Sections 2.10.1 and 2.10.2 of the Final Environmental Impact Statement
(FEIS). These amendments reflect changes in the detailed study alternatives that were an
outcome of the additional alternatives studies described in Section 2.0. The Preferred Alternative
is shown in Figure C-1. The locations of the detailed study alternatives are illustrated in Figure
C-2 to Figure C-5.
CA Oregon Inlet Bridge (Phase 1) Characteristics
The proposed Oregon Inlet bridge (Phase I) would be approximately 2.6 to 3.2 miles (4.2 to 5.1
kilometers) in length. This length is longer than the 2.4 to 2.7 miles (3.9 to 4.3 kilometers) for the
Oregon Inlet bridge in the FEIS. This is because the southern terminus of the bridge was
extended in order to account for sound-side erosion occurring on the north end of Hatteras Island.
The location of the proposed Oregon Inlet bridge was illustrated in Figure 2-6 in the main body of
this EA. The proposed bridge would:
Begin approximately 2,900 to 3,600 feet (883.9 to 1,097.3 meters) south of the southern
terminus of Bonner Bridge. With the Nourishment and Phased Approach alternatives, the
bridge would terminate within the existing NC 12 easement on Hatteras Island. With the
Road North/Bridge South Alternative, it would enter Hatteras Island approximately 260 feet
(79.2 meters) west of Bonner Bridge. With the All Bridge alternative, it would enter Hatteras
Island approximately 350 feet (106.7 meters) west of Bonner Bridge.
At a site visit on July 15, 2009, US Fish and Wildlife Service (USFWS) representatives
identified an additional conceptual design option that would be a minor variation of Phase I
of the Phased Approach alternatives because it would be immediately adjacent to the western
edge of the existing NC 12 easement within which the Phased Approach alternatives would
be built. A variation of that proposal is considered in this Environmental Assessment (EA) as
Phase I of the NC 12 Transportation Management Plan Alternative (Preferred). It would
enter Hatteras Island approximately 212 feet (64.6 meters) west of Bonner Bridge instead of
in the existing easement.
The four alternative termini discussed here for the southern end of the proposed Oregon Inlet
bridge are representative of the range of possible termini, but could change in the context of
additional coordination with the USFWS.
• Follow a curved alignment immediately west of Bonner Bridge. The bridge would cross the
existing navigation channel for vessels using Oregon Inlet approximately 500 feet (152.4
meters) west of Bonner Bridge. The bridge would cross Bridge to Old House Channel,
commonly known as "the crack" where the channel closely parallels Bonner Bridge.
Bonner Bridge Replacement EA C-1 NCDOT TIP Project Number B-2500
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PARALLEL BRIDGE CORRIDOR WITH NOURISHMENT C_2
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Phase 11
Phase III
Phase IV
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RODANITHE
PARALLEL BRIDGE CORRIDOR WITH Figure
PHASED APPROACH C-5
• Terminate at the Bonner Bridge terminus on Bodie Island and follow a route between Bonner
Bridge and the parking lot for the Oregon Inlet Marina and Fishing Center.
C.1.1 Horizontal Alignment
The Oregon Inlet bridge (Phase I) would consist of a southern approach roadway, a southern
approach bridge, main bridge, a northern approach bridge, and a northern approach roadway.
These components as assessed in the FEIS and this EA would be the following lengths:
NC 12
Road Transportation
North/ Management
Bridge All Plan
Nourishment South Bridge Phased Approach (Preferred)
2,270 feet 2,270 feet
Southern (992 meters)- 514 feet 600 feet (992 meters)-
Approach including frontage (157 (183 including frontage 1,460 feet (487
Roadway roads that overlap meters) meters) roads that overlap meters)
most of the most of the
approach bridge approach bridge
Southern 2,410 3,070
Approach 2,000 feet (667 feet feet 2,000 feet (667 800 feet (267
Bridge meters) (735 (936 meters) meters)
meters) meters)
9,987 9,987
Main 9,995 feet feet feet 9,995 feet 9,987 feet
Bridge (3,332 meters) (3,044 (3,044 (3,332 meters) (3,044 meters)
meters) meters)
Northern 3,730 3,730
Approach 31730 feet feet feet 3,730 feet 3,730 feet
Bridge (1,137 meters) (1,137 (1,137 (1,137 meters) (1,137 meters)
meters) meters)
Northern 3,295 3,295
Approach 3,295 feet feet feet 3,295 feet 3,295 feet
Roadway (1,004 meters) (1,004 (1,004 (1,004 meters) (1,004 meters)
meters) meters)
The approach fills (pile of soil upon which the approach roadway is built) as assessed in the FEIS
and this EA would be between the natural ground and a point where the bottom of the bridge
girder can be a minimum of 3 to 6 feet (0.9 to 1.8 meters) above the ground. This distance
between the ground and the bottom of the girder is needed for maintenance access under the
bridge, so girder support bearings are kept above the ground.
C.1.2 Design Characteristics
This section discusses key Oregon Inlet bridge (Phase I) design characteristics related to
navigational clearances and access to recreation opportunities. All other Oregon Inlet bridge
design characteristics identified in the FEIS remain valid with the changes being assessed in this
Bonner Bridge Replacement EA C-7 NCDOT TIP Project Number B-2500
EA. Unless specified, the design characteristics of the Oregon Inlet bridge would accommodate
all the NC 12 Maintenance alternatives.
C.1.2.1 Navigation Clearances
A new bridge across Oregon Inlet must take into account the migratory nature of the navigational
channel. Thus, the bridge should provide the required navigational clearances at spans within the
range of probable channel locations. The proposed bridge would include a series of navigational
spans across Oregon Inlet, a distance up to 3,300 feet [1,006 meters]), with a minimum vertical
clearance of 75 feet (22.9 meters). Spans in the navigation zone would have a minimum of 200
feet (60.1 meters) of horizontal clearance.
Coordination with the US Coast Guard (USCG) and the US Army Corps of Engineers (USACE)
would facilitate the establishment of location(s) for navigation spans, channels, and clearances.
The location(s) of the navigation span(s) would be considered when designing for potential vessel
collision.
C.1.2.2 Access to Recreation Opportunities
A connection from NC 12 to the unpaved beach access road, which is south of the Oregon Inlet
Campground on Bodie Island, would be provided.
Access to the existing fishing parking lot immediately south of Oregon Inlet and the (former)
Oregon Inlet US Coast Guard Station would be provided.
Bonner Bridge has catwalks that are used by fishermen. For safety reasons, access via catwalks
on a new bridge in this corridor is not assumed because the height of the new bridge would put
the catwalks at least 33.5 feet (10.2 meters) above the water. The height would increase the
likelihood of serious, if not fatal, injuries resulting from falls.
Opposition to discontinued fishing access was expressed at the public hearings because fishing is
a popular tourist recreational activity on this part of Hatteras Island. The National Park Service
(NPS) and USFWS have indicated that their objective is to provide for fishing access at the north
end of Hatteras Island at Oregon Inlet, but such access does not have to be provided from
catwalks mounted on the new bridge. One viable approach (except with the Nourishment and
Phased Approach alternatives) appears to be leaving a portion of existing Bonner Bridge for
fishing. A "boardwalk" under and around the new bridge also is a possible option with all of the
Parallel Bridge Corridor alternatives. A boardwalk would be on top of the riprap that currently
blankets the northern shore of Hatteras Island.
With the Phased Approach and Nourishment alternatives only, it is assumed that a temporary
bridge approximately 2,600 feet (793 meters) long would be built east of Bonner Bridge to
maintain NC 12 traffic during construction of the southern end of the new Oregon Inlet bridge.
Once construction of the new Oregon Inlet bridge is completed, a portion of the temporary traffic
maintenance bridge could be retained as a fishing pier to replace the fishing catwalks on Bonner
Bridge. The new fishing pier would be much wider than the existing catwalks (26 feet [7.9
meters] versus 4.5 feet [1.4 meters]), providing fishermen with more room to move about than on
the current catwalks.
Widening a short section of the new structure to provide pedestrian access, separated from traffic
by a barrier, is also a possible option for providing fishing access. Accommodating fishing from
Bonner Bridge Replacement EA C-8 NCDOT TIP Project Number B-2500
the terminal groin is not considered a viable option. Fishing from the groin is considered
dangerous because of the rapid currents adjacent to the groin and the uneven surface of the groin.
The type of access provided will be determined during the final design of Phase I; however,
NCDOT is committed to restoring access to fishing at the northern end of Hatteras Island once
construction of Phase I is complete. The existing catwalks will remain open to the public during
construction as long as it is safely viable.
In whatever way fishing is accommodated, some government body or non-governmental
organization would have to take responsibility for fishing pier or "boardwalk" operation,
maintenance, and liability.
C.2 NC 12 Maintenance Alternatives
C.2.1 Nourishment Alternative
The characteristics and description of this alternative along NC 12 remain as presented in Section
2.10.2.1 of the FEIS. The location of improvements is illustrated in Figure C-2.
C.2.2 Road North/Bridge South Alternative
With this alternative, NC 12 would be placed on a bridge west of Hatteras Island that would begin
with a sweeping curve that connects the bridge directly with NC 12 in Rodanthe, between Sea
Oats Drive and the northern boundary of the Rodanthe Historic District (see Figure 2-1 in the
EA). Users of the bridge going to/from the south on NC 12 would not have to make a turn to
enter onto or exit the bridge. The bridge west of Hatteras Island would continue to the north
through Pamlico Sound, then cross into the Refuge and intersect with existing NC 12 at a point
approximately 2 miles (3.2 kilometers) north of the Refuge's southern boundary. This part of the
island is expected to remain stable with respect to NC 12 through the year 2060; therefore, the
alignment of NC 12 would remain unchanged for 2.6 miles (4.2 kilometers). Beginning at a point
approximately 1.3 miles (2.1 kilometers) south of the Refuge ponds, NC 12 would be relocated to
a point 230 feet (70.1 meters) west of the forecast 2060 high erosion shoreline. This relocation
would continue approximately 6.8 miles (10.9 kilometers) north until the relocated NC 12 would
meet the Oregon Inlet bridge (Phase 1). The location of improvements is illustrated in Figure C-3.
The existing dunes along the oceanside of NC 12 would not be re-built, but would be allowed to
erode naturally. Not re-building the dunes would support Refuge and Seashore policies to let
natural processes take their course. However, three 10-foot-high (3-meter-high) dunes, totaling
2,100 feet (640 meters) in length would be built east of and near the new road in the future, as
conditions warrant. They would be built as the shoreline erodes toward the relocated road and
approaches a distance of 230 feet (70.1 meters) from the pavement. The first dune is expected to
be built by 2030.
The typical section, right-of-way, elevation, design speed, and traffic operation characteristics of
the Road North/Bridge South alternative remain as defined in Section 2.10.2.2 of the FEIS.
Bonner Bridge Replacement EA C-9 NCDOT TIP Project Number B-2500
C.2.3 All Bridge Alternative
This alternative would include the same bridge in the Rodanthe area as described above for the
Road North/Bridge South Alternative. However, instead of relocating NC 12 as a roadway in the
central and northern part of the Refuge, NC 12 would be relocated on a bridge. Two road segments
would be included in this relocation, one near Oregon Inlet and one just north of the Refuge ponds
where access from NC 12 to the Refuge would be provided. Access to the Refuge also would be
available in a 1.8-mile (2.9-kilometer) section of NC 12 that would be left unchanged between the
Rodanthe area bridge and the beginning of the next bridge south of the ponds. The bridges
associated with this alternative would span the five potential breach locations described in Section
2.6.2.3 of the FEIS and would be at least 230 feet (70.1 meters) west of the forecast 2060 high
erosion shoreline. The location of improvements is illustrated in Figure C-4.
The bridges in the central and northern part of the Refuge would begin approximately 1.7 miles
(2.7 kilometers) south of the Refuge ponds. A bridge would continue north for 5.2 miles (8.4
kilometers) to the northern dike of the northern-most pond where a 1,000-foot (305-meter)
section of roadway would be placed. At this location, the Refuge could provide access to the
beach and hiking trails along the perimeter of the northernmost pond. NC 12 would then
continue an additional 1.4 miles (2.3 kilometers) on bridge to a second 1,000-foot (305-meter)
section of roadway. Here, the relocated NC 12 would be connected to the existing roadway,
which would be retained from this point north to the parking lot just south of Oregon Inlet. North
of this second short roadway section, NC 12 would continue northward 0.3 mile (0.5 kilometer)
on bridge to meet the Oregon Inlet Midge (Phase I).
The existing dunes along the oceanside of NC 12 would not be re-built, but would be allowed to
erode naturally. Not re-building the dunes would support Refuge and Seashore policies to let
natural processes take their course.
The typical section, right-of-way, elevation, design speed, and traffic operation characteristics of
the All Bridge alternative remain as defined in the discussion of the Road North/Bridge South
Alternative in Section 2.10.2.2 of the FEIS.
C.2.4 Phased Approach Alternative
Two NC 12 maintenance alternatives are under consideration with the Phased Approach
Alternative (see Figure C-5). They are identical until their southern end within Rodanthe. They
are:
• Phased Approach/Rodanthe Bridge Alternative; and
• Phased Approach/Rodanthe Nourishment Alternative.
C.2.4.1 Characteristics of Phased Approach/RodantheBridgeAlternative
This alternative proposes maintenance of NC 12 in the existing easement by building bridges as
needed. The total constructed length of the Phased Approach/Rodanthe Bridge Alternative would
be 13.7 miles (22.0 kilometers). It would begin in Rodanthe just north of the northern boundary
of the Rodanthe Historic District (see Figure 2-1 in this EA), extend to the north through the
Refuge and across Oregon Inlet, and end on the southern end of Bodie Island approximately 0.2
mile (0.3 kilometer) north of the Oregon Inlet Campground driveway. The total length of the
alternative between the two termini is approximately 15.8 miles (25.4 kilometers), but the
Bonner Bridge Replacement EA C-10 NCDOT TIP Project Number B-2500
constructed length is only 13.7 miles (22.0 kilometers) because of a 2.1-mile (3.4-kilometer)
section of NC 12 in the southern half of the Refuge that would remain because it is not expected
to be threatened by erosion prior to 2060. The bridge would extend a total of approximately 0.8
mile (1.3 kilometers) south of the Refuge boundary into Rodanthe. Drivers would enter and leave
the bridge via a ramp on the west side of the bridge. Access to properties adjacent to the bridge
in Rodanthe would be provided by a one-lane, one-way frontage road on each side of the NC 12
Midge. The two frontage roads would merge back into NC 12 just north of the Rodanthe Historic
District. Crossovers to provide access between the two frontage roads underneath the NC 12
Midge were assumed to be provided in three locations: just south of the Refuge boundary; across
from SR 1445 (Cross of Honor Way); and just north of America Drive. The frontage roads, ramp
down to NC 12, and a typical crossover are illustrated in Figure 2-3 in this EA.
The main bridge would end at a point approximately 420 feet (128.0 meters) north of the district.
The southern end of this bridge would not be brought down to grade; instead, traffic would access
the bridge via a two-lane ramp on the west side of the bridge, which would extend from the
northern district boundary to Cross of Honor Way. The reasons for this configuration are
presented in Section 2.1 of this EA. NC 12 traffic would be at-grade as it passes through the
historic district.
New right-of-way would be required in Rodanthe along most of the length of this alternative to
accommodate the two frontage roads and the exit ramp. From between the northern district
boundary to Cross of Honor Way, the right-of-way width would generally increase from 100 feet
(30.5 meters) to generally 144 feet (43.9 meters), with most of the new right-of-way purchased on
the west side of the existing right-of-way. North of Cross Honor Way, the right-of-way width
would increase to 107 feet (32.6 meters). A temporary construction easement approximately 5
feet (1.5 meters) wide might be needed on both sides of NC 12 for most of the length of the
alternative through Rodanthe.
C.2.4.2 Characteristics of Phased Approach/RodantheNourishmentAlternative
The Phased Approach/Rodanthe Nourishment Alternative would be the same as the Phased
Approach/Rodanthe Bridge Alternative with one exception. The southern end of this alternative
would only extend a total of approximately 0.3 mile (0.5 kilometer) south of the Refuge boundary
into Rodanthe. Because it is substantially shorter than the Rodanthe Bridge Alternative, only one
crossover between the one-way frontage roads would be provided and would be immediately
south of the Refuge boundary.
The same minor amount of additional right-of-way (i.e., approximately 7 feet [2.1 meters]) would
be required along most of the length of this alternative in Rodanthe, with a maximum width of
approximately 147 feet (44.8 meters) required for a short distance at the intersection of the
frontage roads with existing NC 12. The same approximately 5-foot-wide (1.5-meter-wide)
temporary construction easement might be needed on both sides of NC 12 for most of the length
of this alternative in Rodanthe.
South of the bridge, NC 12 in Rodanthe would be protected through 2060 by beach nourishment.
The total required beach nourishment length would be approximately 6,000 feet (1,829 meters),
including 500-foot-long (152.4-meter-long) tapers on each end. Nourishment would extend
approximately 1,500 feet (457 meters) into the Refuge, including the taper of 500 feet (152.4
meters). As with the Nourishment Alternative, it was assumed that nourishment would be needed
every four years. The estimated amount of sand needed for the Phased Approach/Rodanthe
Nourishment Alternative is 2.3 million cubic yards (1.8 million cubic meters) for the first cycle of
Bonner Bridge Replacement EA C-11 NCDOT TIP Project Number B-2500
nourishment, and 1.5 million cubic yards (1.1 million cubic meters) every four years throughout
the life of the project (through 2060).
C.2.4.3 Design Features of Both Phased Approach Alternatives
The design features presented in the section titled "Design Features of Both Phased Approach
Alternatives" beginning on page 2-121 of the FEIS are unchanged.
C.2.4.4 Refuge and (Former) Oregon Inlet US Coast Guard Station Access
The FEIS and this EA assume that four one-lane ramps would be built with the Phased Approach
alternatives to provide vehicular access to and from the parking lot currently used to access the
fishing catwalks on the existing Bonner Bridge and the (former) Oregon Inlet US Coast Guard
Station, accommodating all directions of travel. The ramps would have 12-foot (3.6-meter) lanes
and a 6-foot (1.8-meter) shoulder. One pair of ramps would terminate at the fishing access
driveway, and the other pair would terminate near the road to the (former) Oregon Inlet US Coast
Guard Station. Frontage roads on either side of the bridge and within the existing NC 12
easement would connect the two pairs of ramps. The Phased Approach alternatives would have a
second point of access into the Refuge, within the 2.1-mile (3.4-kilometer) section of NC 12 in
the southern half of the Refuge that would not be threatened by erosion prior to 2060.
C.2.4.5 Construction within the Existing Easement of Pea Island National Wildlife Refuge
The construction description presented in the section titled "Construction within the Existing
Easement of Pea Island National Wildlife Refuge" beginning on page 2-123 of the FEIS is
unchanged.
C.2.5 NC 12 Transportation Management Plan Alternative (Preferred)
The Parallel Bridge Corridor with NC 12 Transportation Management Plan Alternative
(Preferred) does not specify a particular action at this time on Hatteras Island beyond the limits of
Phase I (described in Section C.1 and shown on Figure C-1). Section 2.3.2.2 of this EA presents
a detailed description of how later phases of this alternative would be finalized.
C.3 Conclusion
The amended description of the study alternatives presented in the above section is not
anticipated to create any new, significant impacts not previously identified in the FEIS.
Bonner Bridge Replacement EA C-12 NCDOT TIP Project Number B-2500